1. Field of the Invention
The present invention relates to a decorative sheet which is affixed to an exterior wall surface for decorative and protective purposes.
2. Description of the Prior Art
Conventionally, an exterior wall surface of a building is most typically treated by directly applying a painting or coating material to the surface by means of a spray gun. However, the spray gun method is likely to result in poor appearance due to unevenness of the coating thickness and/or color in addition to giving rise to a pollution problem. Further, the spray gun method is also disadvantageous in that the coating work is greatly influenced by the weather.
To solve the problems of the spray gun method, it has been proposed to use decorative sheets for covering an exterior wall surface of a building. Various kinds of exterior decorative sheets are known, but they are equally impermeable to air and moisture. Indeed, due to the outside use (particularly in consideration of rain), the designing emphasis is placed mainly on durability, and no or little attention has been ever paid to the necessity of imparting an air- and moisture-permeability to the exterior decorative sheet, as opposed to a decorative cloth for an interior wall surface.
When such a decorative sheet is affixed to an exterior wall surface, there is a tendency of locally trapping air between the sheet and the wall surface due to its inability of allowing air passage. As a result, the sheet will be locally bulged in addition to being likely to come off the wall surface. This problem becomes particularly remarkable when the exterior wall surface has projections and depressions.
Further, the prior decorative sheet is known to be relatively hard and heavy. As a result, it is rather difficult to adapt the sheet to corner or bent or undulated portions of an exterior wall surface, and the sheet is likely to displace gravitationally on a vertical wall surface.